A liver nuclear ethanol metabolizing system. Formation of metabolites thatbind covalently to macromolecules and lipids

Recent studies from the laboratory reported the presence in highly purified liver nuclear preparations free of endoplasmic reticulum, mitocondria or c ytosol, of an ethanol metabolizing group of enzymes (NEMS) leading to aceta ldehyde and to hydroxyl and 1-hydroxyethyl (1HEt) free radicals. In the pre sent study it is reported that when NEMS metabolize [C-14]ethanol using NAD PH as cofactor, its reactive metabolites bind covalently to nuclear protein s and lipids. No covalent binding to DNA was detected with presently used p rocedures. The covalent binding to nuclear proteins was acid labile and is mostly attributable to acetaldehyde. Additional evidence was attempted thro ugh studies where the acetaldehyde was identified as its 2,4-dinitrophenylh ydrazone or as its pentafluorphenylhydrazone and gas chromatography (GC) an alysis using electron capture detection. Values obtained were close to dete ction limit and of variable nature. The covalent binding to nuclear lipids involved phospholipids, fatty acids and esters and cholesterol free and est erified and it was only partially labile to acid treatment. Production of e thanol reactive metabolites such as acetaldehyde and free radicals, nearby liver nuclear DNA and nuclear proteins or lipids, might have significant to xicological consequences. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.